Process for the production of alkali perborates and percarbonates

ABSTRACT

ALKALI PERBORATES AND PERCARBONATES ARE SPRAY DRIED BY A PROCESS WHEREIN THE SPRAY CHARGE CONTAINS ONLY THE STABLE BASE COMPONENTS AND THE ACTIVE OXYGEN CARRIER IS DIRECTLY LED INTO THE SPRAY CHARGE BEFORE THE ATOMIZATION AND THE MIXTURE IS THEN SPRAYED AND DRIED IN A SPRAY TOWER.

Jan. 19, 1971 H. PISTOR ETAL 3,555,696

PROCESS FOR THE PRODUCTION OF ALKALI PERBORATES AND PERCARBONATES Filed July 23, 1969 FNVENTOR 8 005'?" Z /s 70A ffu ffirflc was 7.5a

ATTORNEW 1 US. Cl. 34-9 PROCESS Fonrnn PRODUCTION or 'ALKALI" ABSTRACT OF THE DISCLOSURE Alkali perborates and percarbonates are spray. dried by a process wherein the spray charge. contains only the stable base components and the activeoxygen carrieris directly led into the spray charge before the atomization and the mixture is then sprayed and dried in a spray tower.

The present invention is concerned with a process for the production of alkali perborate's and percarbonates by spray drying processes. The alkali perborates and percarbonates (also called alkali peroxoborates and alkali,

carbonate peroxohydrates) are extensively used .for. the production of powdered washing, bleaching and, purifying agents.

For the production of powdered washing, bleaching and purifying agents spray drying processes are em ployed predominantly. In these processes a spray charge consisting of an aqueous solution of the active washing agent, washing assistant agent and additives is atomized through a spray device in a tower. Hot air is injected into United States Patent the spray tower inorder to removeexcess water. There is obtained a dry,vo 1uminous powder, the so-called spray product. Since the active oxygen containing compounds such as alkali perborates and percarbonates necessary as the bleaching constituents are inclined to be destroyed by the action of elevated temperatures and thepresence of certain other chemicals these' bleaching agents are generally added subsequent tothe spray product.

.The usual method for the productionro f' alkali perborates or percarbonates consists of reacting. the alkali I borate or carbonate with hydrogen peroxide, in aqueous solution whereby the active oxygen containing' com-" pounds precipitateas a 'crystallineproduct i They" are separated olf and carefully dried, I.

It. is detrimental to the mixing 'of thespray product andthe active oxygen containingcompounds,that the ininform and density on account of their difier'eiit methods of production as a result'of which it is diflicult to obtain homogenous mixtures.

' .To eliminate'thisadvantage of different granular dividual particles ofboth components are very difierent ture between the washing agent-spray .product aiid .the'

bleaching agent it was attempted to likewise prepare the perborate and percarbonate by spray drying v processes.

However, great diliiculties were encountered. On,ac-

count, of the relatively diflicultsolubility of alkali perborate or percarbonate in a spray charge it is necessary to operate .With very dilute solutions, a bout 2-4- weight percentaqueous solutions. If the temperature of the spray charge is raised in order to increase the solubility a destruction of the active oxygen already occurs in the solution being sprayed.,This leads toactive oxygen loss 'and' to irregularity in the spraying process. c

It has now been found that alkali perborates or percarbonates can be produced inspraying drying processes it the spray charge only contains th e stable base compo- (see, for Technischen Chemie, vol. 1, page 603 and page 729 ii).

3,555,696 Patented Jan. 19, 1971 ice prepared for example sodium perborate, potassium perborate, sodium percarbonate and potassium percarbonate.

The stable base components are present as aqueous solutions in concentrations of 20 to 100 weight percent, in other words, the base components are capable of addition as aqueous or water free melts.

Unless otherwise indicated, all parts and percentages are by weight.

The active oxygen carrier, of which hydrogen peroxide is most important are generally added in aqueous solutions of 25 to weight percent although the concentration can range from 5 to 95%. In place of hydrogen peroxide, there can be used alkali peroxides, as sodium peroxide. These solutions can be made stable by the addition of alkali or alkaline earth silicates or phosphates, e.g., sodium silicate, potassium silicate, sodium meta silicate, calcium silicate, sodium pyrophosphate, potassium pyrophosphate, sodium ortho phosphate, potassium ortho phosphate or alkaline earth halides, e.g., magnesium chloride.

As base components there can be employed alkali borates and carbonates, e.g., sodium metaborate, borax, potassium metaborate, potassium tetraborate, sodium carbonate, potassium carbonate, sodium bicarbonate and potassium bicarbonate. The base components can be added as such or in the form of alkali hydroxides, e.g.,

, sodium hydroxide or potassium hydroxide and borax or carbon dioxide or boric acid.

The atomization is carried out with conventional nozzles, preferably with compressed air atomization, above all if the materials to be sprayed are not highly fluid example, Ullmann, Enzyklopedie der The temperature of the drying air is 602-00 C., that of the exit air which corresponds to about that of the sprayed product to about 40-100 C.

It is also possible to use for the spray charge not the entire base components but only a partial component,

. i.e., either only the alkali portion or only the acid residue as the borate or carbonate components, as an additive to the spray charge and afterwards mix the second component with the active oxygen carrier.

. The technical advance of the process of the invention lies inthe possibility of spraying alkali perborate or percarbonate without-increased loss of active oxygen occurring as is the case with the customary crystallization process. The loss is 5 to 8%. The per compounds accumulate furthermore in such particle size that they can be homogeneously mixed with other washing agent con- .stit-uents rwithout difiiculty.

, The process is especially suited for the production of products containing small quantities of water of crystallization with correspondingly high active oxygen contents.

By dilution with inorganic salts which are added in the spray charge, it is possible to make up lower active oxygen content products. Examples of such inorganic salts are sodium sulfate, vpotassium sulfate, sodium carbonate, potassium carbonate, sodium orthophosphate, potassium orthophosphate. When such inert salts are added they can be used in an amount of 2 to of the total composition.

The process of invention will be best understood in connection with the drawing and following examples.

The single figure of the drawing is a schematic diagram of an apparatus suitable for use according to the invention.

Referring more specifically to the drawing, there is...

EXAMPLE 1 In order to produce a spray charge 134.3 parts by weight of sodium metaborate (NaBO was dissolved with heating to 40 C. in 289.7 parts by weight of water. This solution was sprayed into an atomization" drier over a period of 45 minutes. Shortly before the spray nozzle (about 6 inch) to the spray charge, there was homogeneously added 292 parts of hydrogen peroxide (23.7 weight percent in water), which contained 0.4% magnesium chloride (Mgcl The temperature of the drying percent) The temperature of the dryingair amounted to air amounted to 98 C. at the entrance to the tower and to 50 C. at the exit. There was obtained 206 grams of sodium perborate with an active oxygen content of 15.04% which corresponds to a yield based onthe active oxygen of 95%.

EXAMPLE 2 To produce a spray charge 252 parts by weight of sodium metaborate (NaBO and 137 parts by weight of sodium sulfate (Na SO were dissolved in 1036 parts by 'weight of water with heating to 40 C. This solution was processed in the course of an hour in an atomization drier while there was added homogeneously to the liquid stream shortly (6 inch) before the spray nozzle 282 parts by weight of hydrogen peroxide (49 weight percent) which contained 0.5% magnesium chloride. The temperature of the drying air at the entrance to the tower was 163 C. and at the exit 93 C. There was obtained 544 grams of sodium perborate with an active oxygen content of 11.00%, corresponding to an active oxygen yield of 92%.

"EXAMPLE 3 1094 parts by weight of potassium meta'borate (KBO were dissolved in 1734 parts by weight of water and cooled to 20 C. to form a spray charge. The solution was sprayed into an atomization drier in the course of 195 minutes. Shortly (6 inch) before the spray nozzle 2660 parts by weight of hydrogen peroxide (34.4 weight percent) containing 0.5% magnesium chloride (MgCI were homogeneously added. The temperature of the drying air at the entrance to the tower amounted to 103 C. and at the exit to 71 C. There were obtained 2030 grams of potas sium perborate with an active oxygen content of 20.11%, corresponding to an active oxygen yield of 95%;

EXAMPLE 4 :This:solution was added to a spray towen-inthe course of to a yi eIdlof 95%, b'as fed on the active oxygen. f

EXAM L a spray charge 18.3 parts by lwei'ghtof sodiurn hydroxide (NaOI-L) were dissolvedin 91,5 parts by weight of water. This solution was sprayed into an atomization drier' in the course of 65 minutes. Shortly ('6inch). before the spray nozzle, there were h m gene usly dd d 87.2 parts by weight of borax (Na B O;, -10H Q) dissolved in 92.3 pa rfs'lby-weigh'tfof hydrogeni'peroxide (.35 weight 90? "the entrance: tothe tower and i048 C. atthe ex't Thereywere obtained 101 grams of. sodium perborate with an active oxygen content of 14.5% corresponding to i an active oxygen yield of 96% J.

concentration of 20'to 100%.

261.3 parts by weight of sodium carbonate (Na cO 42.7 parts by weight of sodium bicarbonate (NaHCO and 1.2 parts by weight of sodiumpyrophosphate (Na P O were dissolved in 1188.8 parts of water with heating and then cooled to 18 C. to form a spray charge.

" What is'claim'ed is:

1. A process for spray drying alkali perborate or'a'lkali percarbonate comprising employing as a spray charge the stable base component and adding the active oxygen carrier immediately before the atomization of the spray charge in the' sp ray tower andthere'afte'r drying the mix ture.

2.'A process according to claim 1 wherein hydrogen peroxide is the active oxygen carrier. p 3. A process according to claim 1 wherein the spray charge contains onlythe acid or the alkali component of the 'b'orate -or'carli'onate and the other of the alkali or acid component isadded with the active. oxygen carrier *4. A process according to claim 3 wherein the active oxygen carrier is hydrogen peroxide.

A process'according to claim 11 wherein the base component conatinsalkali metal bora'te or carbonate." 6: A process according to claim 1 wherein the spray charge is in the {formof *an aqueous solution having a 7'. A process according to claim 6 wherein the active oxygeii'carrier' is hydrogen'peroxide and the drying tem per'atuteis'60to'200C. i 8. A process according to claim 1 wherein {an inert salt is included in the components 'to be'-"s'prayed.

T" References Cited- @U I ED "STATES AT N 92,232,727 2/1941} Peterkin et al.

3,340,567 9/19'67 Flack "at. 34-. 9 X 

